That's not a null pointer. Address `0` can be valid. A null pointer critically does not compare equal to any non-null pointer, including a pointer to address 0

That's not a null pointer. Address `0` can be valid. A null pointer critically does not compare equal to any non-null pointer, including a pointer to address 0 on platforms where that's allowed. > An integer constant expression with the value `0` , such an expression cast to type `void *` , or the predefined constant `nullptr` is called a null pointer constant ^69) . If a null pointer constant or a value of the type `nullptr_t` (which is necessarily the value `nullptr` ) is converted to a pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal to a pointer to any object or function. C 23 standard 6.3.2.3.3 Also this is point 6 in the article.